We had a compass adjuster named Captain Barber on one of my boats, swinging the compass. He had some interesting points to make . When asked about flux gate compasses, he said "Those make more work for me than they take away. A steel boat will swing a compass at 100 yards. People buy the flux gate at huge expense, give up trying to get them to work, then give me a call." He said the balls work upright, but heeling throws them out. What it takes to deal with heeling is a magnet dead centre, right below the compass.
He said the dome compasses have a power factor of about 8. Card compasses ,the Seattle made Dirigo being one of the best , have a power factor of about 400 .
When asked to check out a Dirigo, he took his steel tape measure and moved it towards, and away from the compass. He said if you pull the compass of course and it goes right back to where it was, the pins are good. If it stays off a by a few degrees, the pins are worn. One way to avoid damaging the pins is to mount it on foam rubber, as vibration is what dulls the pins. However, I believe the constant motion of a sailboat at sea will nullify the effect of resistance in the pins. Flat sea in a fog bank in our protected inside waters may be a problem with a sticky compass tho.
I have found my Autohelm very forgiving in its proximity to steel . It has never locked in . I have heard other brands like Tillermaster and Navico have problems in a steel boat. One of my 36 footers had the autohelm along side the wheelhouse side, 3 inches from the steel with no problems, going from BC, to Mexico, to Hawaii, to Alaska and home again. Other brands , I have been told, would not work so close to steel.
With GPS, you can check your compass on any course, by comparing it to the GPS, and writing it down,. not an option in the past.
With an autopilot, sometimes the buttons stick, throwing the helm hard over. Usually this happens when you first turn them on. I suspect that may be what happened when pleasure boats suddenly swung 90 degrees into the path of BC ferries in recent years, resulting in several deaths.One should never use an autopilot ,unattended, in crowded waters .
Thanks for the question on the subject of steel boats. Its a breath of fresh air, after Bob's frequent name calling , baby pictures, pool pictures, food and booze postings, plastic boat postings , and constant attempts to change the subject to something which has nothing to do with the original question, all to cover his almost complete lack of knowledge of steel boats.
You're welcome for the subject contents but you really didn't answer my questions.
How badly does a steel boat affect compass deviation compared to other hull materials? And does a steel hull affect autopilot systems that have those compass computers?
You gave some info on swinging the compass and even mentioned the balls, but can they be compensated to minimal deviation when mounted in a steel hull as well as in other materials. I know you have no love for, nor experience with "plastics" or wood so I'm not sure you can answer this.
Some fellow intimated that fluxgate compasses are worthless on a steel hull. Aren't those the type of compasses that many autohelms use? I could be mistaken in that.
You said "I have found my Autohelm very forgiving in its proximity to steel ." but you didn't mention a brand. Are there autohelms that are manufactured specifically for use in a steel hull?
Your last paragraph was useless. You placed me on Bob and Smack's team earlier if you will recall.